Process-based Modeling of Ammonia Emission from Beef Cattle Feedyards with the Integrated Farm Systems Model

Variability of Ammonia and Methane Emissions from Animal Feeding Operations in Northeastern Colorado

Concentrated animal feeding operations (CAFOs) are major emitters of both ammonia (NH₃) and methane (CH₄). However, current emission inventories have limited temporal resolution and use data derived from a small subset of farms. To this end, we deployed three mobile laboratories during the DISCOVER-AQ campaign in summer 2014 with a focus on northeastern Colorado. Observations of NH₃ and CH₄ plumes downwind of 43 CAFOs were used to investigate the diurnal and site-to-site variability of emissions with an inverse area source plume modeling approach. Ammonia emissions scaled to all permitted animals in Weld, Morgan, and Larimer counties were estimated at 1.9 Gg month^-1, 50% greater than the U.S. NEI 2014 and 360% greater than EDGAR for the month of August. Methane emissions were likewise estimated at 10.6 Gg month^-1, consistent with the U.S. GHGI but 99% greater than EDGAR. Significant differences between individual CAFOs with repeat observations were also observed for both CH₄ and NH₃ emissions. The large subfarm, site-to-site, and diurnal variabilities observed show the importance of measurements taken across these scales in order to derive representative emission factors.

Use of new technologies to evaluate the environmental footprint of feedlot systems

With increased concern over the effects of livestock production on the environment, a number of new technologies have evolved to help scientists evaluate the environmental footprint of beef cattle. The objective of this review was to provide an overview of some of those techniques. These techniques include methods to measure individual feed intake, enteric methane emissions, ground-level greenhouse gas and ammonia emissions, feedlot and pasture emissions, and identify potential pathogens. The appropriate method to use for measuring emissions will vary depending upon the type of emission, the emission source, and the goals of the research. These methods should also be validated to assure they produce accurate results and achieve the goals of the research project. In addition, we must not forget to properly use existing technologies and methods such as proper feed mixing, feeding management, feed/ingredient sampling, and nutrient analysis.

Cradle-to-farm gate environmental footprints of beef cattle production in Kansas, Oklahoma, and Texas

A comprehensive national assessment of the sustainability of beef is being conducted by the U.S. beef industry. The first of 7 regions to be analyzed is Kansas, Oklahoma, and Texas. A survey and visits conducted throughout the region provided data on common production practices. From these data, representative ranch and feedyard operations were defined and simulated for the varying climate and soil conditions throughout the region using the Integrated Farm System Model. These simulations predicted environmental impacts of each operation including cradle-to-farm gate footprints for greenhouse gas emissions, fossil-based energy use, nonprecipitation water use, and reactive N loss. Individual ranch and feedyard operations were linked to form 28 representative production systems. A weighted average of the production systems was used to determine the environmental footprints for the region where weighting factors were developed based on animal numbers reported in the survey and agricultural statistics data. Along with the traditional beef production systems, Holstein steer and cull cow production from the dairy industry in the region were also modeled and included. The carbon footprint of all beef produced was 18.3 ± 1.7 kg CO2 equivalents (CO2e)/kg carcass weight (CW) with the range in individual production systems being 13 to 25 kg CO2e/kg CW. Energy use, water use, and reactive N loss were 51 ± 4.8 MJ/kg CW, 2,470 ± 455 L/kg CW, and 138 ± 12 g N/kg CW, respectively. The major portion of each footprint except water use was associated with the cow-calf phase; most of the nonprecipitation water use was attributed to producing feed for the finishing phase. These data provide a baseline for comparison as new technologies and strategies are developed and implemented to improve the sustainability of cattle production. Production information also will be combined with processing, marketing, and consumer data to complete a comprehensive life cycle assessment of beef.

Livestock GRACEnet: A Workgroup Dedicated to Evaluating and Mitigating Emissions from Livestock Production

Ammonia, greenhouse gases, and particulate emissions from livestock operations can potentially affect air quality at local, regional, and even global scales. These pollutants, many of which are generated through various anthropogenic activities, are being increasingly scrutinized by regulatory authorities. Regulation of emissions from livestock production systems will ultimately increase on farm costs, which will then be passed onto consumers. Therefore, it is essential that scientifically based emission factors are developed for on-farm emissions of air quality constituents to improve inventories and assign appropriate reduction targets. To generate a larger database of on-farm emissions, the USDA-ARS created the workgroup Livestock GRACEnet (Greenhouse gas Reduction through Agricultural Carbon Enhancement Network). This introduction for the special section of papers highlights some of the research presently being conducted by members of Livestock GRACEnet with the intent of drawing attention to critical information gaps, such as (i) improving emissions measurements; (ii) developing emissions factors; (iii) developing and validating tools for estimating emissions; and (iv) mitigating emissions. We also provide a synthesis of the literature with respect to key research areas related to livestock emissions, including feeding strategies, animal housing, manure management, and manure land application, and discuss future research priorities and directions.